1. Field of the Invention
This invention relates to a developing assembly, and a developer carrying member, by means of which a latent image formed on an electrostatic latent image bearing member by electrophotography, electrostatic recording, magnetic recording or the like is developed by the use of a developer to render it visible.
2. Related Background Art
Polymers having a hydrophilic group such as a sulfonic acid group are expected to be applicable to various uses.
The synthesis of such polymers having a sulfonic acid group is commonly limited to what uses specific vinyl monomers containing a sulfonic acid functional group. Specific examples of such monomers may include sulfonated styrenes, or AMPS (2-acrylamido-2-methylpropanesulfonic acid). These are disclosed in, e.g., Japanese Patent Application Laid-open No. 2002-351147.
As for developing assemblies by means of which electrostatic latent images formed on the surface of a photosensitive drum serving as the electrostatic latent image bearing member are rendered visible by the use of a toner, which is a one-component developer, there are conventionally those utilizing a system in which the mutual friction between toner particles themselves, the friction between a developing sleeve as the developer carrying member and the toner particles and the friction between a member which controls the toner coat level on the developing sleeve (a developer layer thickness control member) and the toner particles are utilized to provide the toner particles with positive or negative electric charges, the toner thus charged is applied very thin on the developing sleeve and then transported to a developing zone, and, in this developing zone, the toner is attracted and adheres to electrostatic latent images on the surface of the photosensitive drum to render the electrostatic latent images on the photosensitive drum visible as toner images.
In such conventional developing assemblies described above, developer carrying members are used which are obtained by molding a metal, an alloy or a metal compound into a cylinder and treating its surface by electrolysis, blasting, filing or the like so as to have a stated surface roughness. Meanwhile, in recent years, toners are desired to have a small particle diameter in order to fix developers at low temperature as required for energy saving and to achieve the formation of high definition images. In such toners having small particle diameter, the toner has such a large surface area per unit weight as to tend to have great surface electric charges, and may cling to the developer carrying member because of what is called a charge-up phenomenon, so that the developer having come to be newly fed onto the developer carrying member may be charged with difficulty and the developer is apt to have non-uniform charge quantity.
To cope with this problem, as disclosed in Japanese Patent Application Laid-open No. H01-277256, a method is proposed in which, in order to prevent the developer from having such excess electric charges or prevent the developer from adhering strongly to the developer carrying member, a film or coating (a resin layer) composed of a resin composition obtained by dispersing in a resin a powder of a conductive substance such as carbon or graphite or of a solid lubricant is formed on the developer carrying member. In Japanese Patent Application Laid-open No. H02-304468, a developing sleeve is proposed which has a metallic substrate and provided thereon a conductive resin layer comprising a resin coating layer in which a solid lubricant, a conductive fine powder such as carbon and spherical particles have been dispersed. Also, in Japanese Patent Application Laid-open No. H08-240981, a developing sleeve having a surface layer is proposed in which spherical particles are dispersed in a conductive coat layer so that wear resistance can be improved and the shape of the developing sleeve surface can be made stable, and also so that the charging of the toner can be improved, and the developing sleeve can be kept from being contaminated by the toner or from toner melt adhesion even where the conductive coat layer resin layer has somewhat worn.
These proposals, however, have not been sufficiently effective in overcoming the problems.